A typical kaleidoscope consists of two or more elongated, planar mirrors positioned side-by-side, lengthwise, each pair touching at one long edge and inclined at a fixed angle with respect to each other. The reflecting surfaces of the mirrors are located on the inside of the "V" that is formed from each adjacent pair of mirrors. Most common kaleidoscopes contain two mirrors, typically at an angle of 36.degree., 45.degree. or 60.degree. with respect to each other, or three mirrors at 60.degree. with respect to each other. The cross-section in the latter case is an equilateral triangle. Generally, the mirrors are housed in a tubular container, to which they are fixedly attached. In this specification, the container will be referred to as a "tube". Usually, but not necessarily, the tube is cylindrical.
Generally, one end of the tube is blocked off with opaque material, but contains an opening for looking into. Occasionally, this opening contains a lens, but generally it does not. This viewing hole, with or without a lens, is usually referred to as the "eye-piece," and it will be so referred to in this specification. The eye-piece is positioned so that one can look down the trough between the reflecting surfaces of the mirrors.
The opposite end of the tube generally consists of a receptacle containing movable objects. This receptacle is attached to the tube. The end of the receptacle closest to the eye-piece is usually transparent, and the opposite end is usually translucent. The other sides of the receptacle may be transparent, translucent, or opaque. In the literature of kaleidoscopes, this receptacle is generally referred to as the "object box" or "object cell," and the items within the receptacle are referred to as "objects". The terms "object cell" and "objects" will be used in this specification.
Most frequently the objects consist of colored solids such as glass, plastic, or stone. Sometimes common household items such as paper clips, rubber bands, etc. are used for objects.
When in use, the kaleidoscope is usually held essentially horizontally. When one looks into the eye-piece, one sees a symmetrical design based on the objects that are in the object cell. The symmetrical design results from directly viewing the objects in the object cell that lie in the area corresponding to the trough of the mirrors in conjunction with the multiple reflections of those objects in the mirrors. The cross-sectional area of the object cell that is directly visible by looking through the eye-piece is referred to as the "direct field of view" in this specification.
By rotating the kaleidoscope, the objects in the object cell are allowed to tumble about and fall into new, random arrangements, thus giving rise to an infinite number of possible symmetrical designs. For some kaleidoscopes, the object cell is rotatably attached to the tube such that the object cell can be rotated about the longitudinal axis of the kaleidoscope while the mirrors are maintained essentially stationary. The "longitudinal axis" is defined as the axis that extends symmetrically, or essentially symmetrically, along the length of the tube. In this case, various designs can be generated by rotating the object cell alone, rather than rotating the kaleidoscope as a whole.
Modifications of the kaleidoscope in which the object cell rotates about an axis that is orthogonal to the longitudinal axis of the kaleidoscope are described by Stough in U.S. Pat. No. 1,078,008 and by Forsee in U.S. Pat. No. 3,756,685. In some kaleidoscopes, the object cell is removable from the tube of the kaleidoscope, and some kaleidoscopes contain a set of replaceable object cells.
The object cell of some kaleidoscopes consists of a liquid-tight container or segmented container, and the objects consist of a liquid or liquids. Descriptions of such liquid-containing kaleidoscopes are given by Knittel in U.S. Pat. No. 3,039,356, by Powers in U.S. Pat. No. 3,383,150, and by Orans in U.S. Pat. No. 3,748,013. The kaleidoscope that is described by Knittel contains an object cell that is rotatable with respect to the tube about the longitudinal axis. The object cell in that kaleidoscope is partly filled with a liquid, and the object cell contains a number of baffles which cause the liquid to be scooped up and spilled as the object cell is rotated. This movement of the liquid generates a moving, symmetrical design that is visible through the eye-piece. In column 4, lines 5 through 21 of U.S. Pat. No. 3,039,356, Knittel explains how different types or styles of designs are produced in this particular kaleidoscope depending on whether the object cell is rotated while the tube is held stationary or the kaleidoscope as a whole is rotated.
The theory of kaleidoscopes is described in a number of textbooks on optics, such as: "Mirrors, Prisms and Lenses", 3rd edition, by J. P. C. Southhall, Macmillan Co., New York, 1933, pages 43-51, and "Curiosities of Light Rays and Light Waves" by S. Tolansky, American Elsevier Publishing Co., New York, 1965, pages 20-24. An article by J. Walker in Scientific American (Dec. 1985, Vol. 253, No. 6, pages 134-138, 144, 145) further discusses the theory of kaleidoscopes. A book entitled "Through the Kaleidoscope" by Cozy Baker (Beechcliff Books, Annapolis, Md., 1985) describes many kaleidoscopes that are currently available on the market.